Taxpayers need a bill of rights from the Internal Revenue Service so that they will know what the IRS can — and can't — demand of them, according to the Taxpayer Advocate's 2013 report to Congress. And the IRS needs more funding if it's to offer meaningful help to citizens.

The IRS collects an estimated 85.5% of what is owed, and 98% is collected voluntarily — that is, without the IRS taking special collection efforts through liens and other measures. By and large, people pay the taxes they owe, the report says.

But the complexity of the tax law means that people need help filling out their taxes, and the IRS is increasingly falling short of giving that help. In 2013, the IRS received 109 million telephone calls, but only 61% of those seeking help got through, the report says. Average wait time: 17.6 minutes on hold, up from 2.6 minutes in 2004. In an effort to reduce hold periods, the IRS will answer only basic tax questions, and not detailed ones, in 2014.

IRS performance via mail and walk-in assistance has fallen as well. "The IRS has abandoned return preparation in its walk-in sites, which was already limited to the most vulnerable populations of taxpayers — the elderly, the disabled, and the low income," the report says.

A big part of the problem: More returns, fewer employees, and drastic cuts in money for training employees. The IRS workforce has fallen from to 87,000 full-time workers from about 95,000 in 2010. The training budget has fallen 87%, to about $22 million. "Thus, the IRS not only has fewer employees than four years ago, but those who remain are less equipped to perform their jobs," the report says.

Most importantly: Taxpayers need a bill of rights, spelling out what the IRS can and can't demand of them. Citizens should not only pay the taxes they owe, but not pay more than they do owe, the report says.